How to Trim an Audio File (Without Re-Encoding)

The part you want is usually a small part. Four minutes of a ninety-minute lecture. The chorus that starts at 1:12. Thirty seconds of a song, for a ringtone. Everything else is in the way — and clearing it out shouldn't cost you any of the audio you're keeping. This guide covers how to trim an audio file with the MyTools audio trimmer: the four moves that do it, and the one switch in the sidebar that quietly decides whether your MP3 comes out as an untouched copy or a fresh encode.

Cutting an audio file, in four moves

1. Drop the file in

The page opens on a drop zone that takes one file at a time, up to 200 MB. MP3, WAV, M4A, FLAC, OGG, AAC, Opus, AIFF, WMA and WebM all load. The real test is whether your browser can decode the format, because the decoding happens on your own machine — the file is handed to the page, not sent anywhere, which is why even a 180 MB file is ready the instant you drop it.

2. Mark the part you're keeping

Once the audio decodes you get a waveform of the whole track, a two-handled timeline beneath it, and a settings column. Three ways to set the range, and you can mix them:

• Drag the handles. Left is your start, right is your end. The selected stretch stays bright while the rest of the waveform dims, so the shape of what you're keeping is visible before you commit to anything.
• Type the timestamps. The Start and End fields take 1:12.400, 0:45, 1:02:30, or a bare 95 for ninety-five seconds. Press Enter to commit.
• Drag, then type. Get close with the handles, then fix the exact millisecond in the fields. The slider itself steps in thousandths of a second.

Preview selection plays only the range you've marked, on loop, with a playhead crossing the waveform as it goes. Use it — it's the fastest way to catch a start point that eats the first syllable. The sidebar shows the running length next to Length.

3. Decide about the fades

Two switches, Fade in and Fade out, each applying a 50-millisecond ramp at the corresponding edge. That's a de-clicker, not a musical fade: it kills the pop you hear when a cut lands mid-waveform. It also changes what the tool does under the hood, which is the next section.

4. Trim, then download

Click Trim audio. The first cut of a session spends a few seconds pulling in the audio engine that does the work locally; after that it starts straight away and reports a percentage as it runs. What comes back is yourfile-trimmed.mp3 — same extension you put in, no conversion. Trim again drops you back into the editor with the file still loaded, which is the quick way to pull several clips out of one recording without re-adding it each time.

The fade switches are also a quality switch

With both fades off, the trimmer copies the encoded audio straight across. Nothing is decoded and nothing is re-encoded — the bytes you keep are the bytes you had, and the cut takes about as long as reading the file.

Turn either fade on and that stops being possible. Applying a ramp means decoding the audio to samples, multiplying it, and encoding it again. For WAV and FLAC that costs nothing but time: they're lossless, so a second pass is identical. For MP3, M4A and OGG it's a second lossy generation. On a ringtone or a podcast teaser you won't hear it. On a master you plan to edit further, it's worth knowing you spent a generation on a 50-millisecond de-click.

The copy mode has one quirk of its own. Encoded audio is stored in frames, and a copy has to cut on a frame boundary rather than at the exact instant you typed. An MP3 frame at 44.1 kHz holds 1152 samples — about 26 milliseconds. AAC frames hold 1024, roughly 23. So a copy-mode cut can sit up to one frame off your number. PCM WAV has no such frames and lands exactly where you ask.

Twenty-six milliseconds is inaudible on speech. It's about a fifth of a sixteenth note at 120 bpm, which is enough to sound like a stumble if you're cutting a music bed to a beat. That's the one case where you preview instead of trusting the timestamp.

How long should the clip be?

• Ringtone — 30 seconds. iPhone ringtones cap out at 40, so 30 is the safe target. Start where the hook lands, not where the song does.
• Podcast or trailer teaser — 45 to 60 seconds. Long enough for one complete thought from the guest, short enough to be posted rather than skipped.
• Study or lecture excerpt — the explanation, plus five seconds either side. Cuts that begin on the first syllable sound clipped. Leave air at both ends.
• Anything going into a video — trim the audio a beat longer than you think you need. Tightening later is free; finding the missing half-second is not.

Trimming shrinks the file in proportion to time, since the bitrate never changes. A 3-minute MP3 at 320 kbps is roughly 7.2 MB; keep 30 seconds of it and you land near 1.2 MB. If you're cutting to hit an upload limit rather than to hit a length, that ratio tells you straight away whether trimming alone gets you there.

When it doesn't behave

The waveform never appears. The decode failed — WMA and some AIFF variants are the usual suspects, and support varies by browser. If the browser can still play the file, the duration and the time fields keep working and you're only missing the picture, so lean on Preview selection. If it can't play it either, that format is a dead end in that browser; try another one.

Trim audio stays greyed out. Your selection is under the 100-millisecond minimum. Widen it, or check that you didn't type an end time that sits before your start.

The part you want to delete is in the middle. A trim keeps one unbroken range, so a middle cut is really two exports: mark everything up to the bad patch and download that, hit Trim again to reload the same file, mark everything after it and download that too. The audio merger glues the halves back together, and the seam lands wherever you put it.

The file is too big, or the clip still is. Trimming removes seconds, not bitrate. A stereo 44.1 kHz WAV runs about 10 MB per minute, so the 200 MB ceiling arrives near the 20-minute mark; past that, the file needs compressing before it will open. And once a clip is as short as it can usefully be, changing its size per second is the audio compressor's job, not the trimmer's.

Most of the time this isn't editing at all. It's deciding where the useful part starts and where it stops, and getting everything else out of the frame — a two-handle problem, done in about a minute.

Open the audio trimmer →